The invention relates to a crane structure for loading and unloading cargo or other items onto or from a ship or other cargo-carrying vehicle. More particularly, the invention relates to such a crane structure which is itself mounted on a transport vehicle and includes a movable horizontal boom or gantry structure and apparatus and mechanism for allowing the gantry structure to be altered for transport. In particular, the crane structure can be rotated so that the gantry structure is in a position parallel to the direction of travel of the transport vehicle and the overall height and width of the crane structure can be reduced to allow travel of the entire transport structure under bridges or through narrow passageways.
It is frequently desirable or necessary to load or unload a large ocean going transport ship so that the cargo (e.g. bulk goods) can be transported through shallow rivers and other waterways by barges and the like. It is also desirable at times to load or unload the transport ship at an off-shore position away from stationary docking facilities. Accordingly, large gantry-type cranes have been mounted on tower structures attached to floating barges so that the cranes may be moved into positions adjacent such ships thus allowing cargo or other items to be loaded or unloaded between the ships and separate cargo barges. Such prior crane structures, however, have suffered the disadvantages of being insufficient in either overall height or trolley travel to clear or efficiently load or unload the very large ships now commonly in use. Alternatively, if such crane structures are built with sufficient height, trolley travel and size to be usable with such ships, they are frequently limited to use in a specific locality because of the inability to be transported under bridges or through relatively narrow waterways. The need has thus arisen for such a large crane structure that is equipped with apparatus for selectively decreasing the overall height and the overall width dimension perpendicular to the direction of travel.
In accordance with the present invention, a gantry-type crane structure is attached to the top of a vertical tower structure which is mounted on a transport vehicle, preferably a floating barge or other vessel. The boom portions are also preferably supported or anchored by an upper supporting structure attached to the top of the tower structure. The tower structure is adapted for rotation on the transport between a first position wherein the outer boom portions of the gantry protrude outwardly in horizontal directions perpendicular to the direction of travel of the vessel and a second position wherein the boom portions are aligned with the direction of travel of the vessel. In addition to such rotational capability, the preferred tower structure is adapted for linear travel along the transport vehicle and includes self-contained operating apparatus. The crane structure is also preferably equipped with means for lowering the outwardly-protruding boom portions as well as for lowering or collapsing the upper supporting structure on the top of the tower structure. Thus, the overall height and width of the crane may be significantly reduced in order to allow sufficient clearance under bridges or other overhead obstructions and through narrow passageways.